Packaging tray and method of manufacture

ABSTRACT

Thermoplastic packaging trays are provided that are filled with a product and wrapped in film, and methods of producing the tray with a peripheral edge region that avoids tearing of the overwrap film. In various embodiments, the tray has a beaded, a flat, or a combined beaded and flat peripheral edge.

FIELD OF THE INVENTION

The present invention relates to plastic packaging trays that are filledwith a product and wrapped in a plastic overwrap film, and methods ofproducing the tray with a peripheral edge region that avoids tearing ofthe overwrap film. In various embodiments, the tray has a beaded, a flator a combined beaded and flat peripheral edge.

BACKGROUND

Thermoformed plastic trays are commonly used for packaging food, e.g.,meat or produce, and other products. These trays are designed to befilled with a product and the filled tray then wrapped in a plasticfilm. However, the thermoforming process typically creates a very sharpperipheral edge on the thermoformed tray, either as formed or aftercutting excess material from around the periphery of the tray, that willtear the film and thus expose the product in the package to spoilage orcontamination. Tears can occur either during the wrapping process, orduring handling and distribution to the consumer.

Prior attempts to form a smooth edge are often performed in thethermoforming mold, a hot forming process that involves further bendingof the tray periphery so that it is disposed underneath the tray flange,adjacent the body of the container. However these processes requireexpensive equipment that must accommodate thermoforming, cutting andbending processes and as a result greatly increase not only theequipment cost but also the production time and cost of the finishedtray.

SUMMARY OF THE INVENTION

The present invention relates to various embodiments of a plasticpackaging tray, configured to be filled with a product and wrapped inplastic film, and methods of producing the tray with a peripheral edgeregion that avoids tearing of the overwrap film. The tray can be formedwith a beaded, a flat, or a combined beaded and flat peripheral edge,each formed by a cold pressing process, which does not require a heatingstep and thus substantially reduces the cost of equipment and processingtime.

In one embodiment, the plastic tray is produced from an intermediateplastic thermoformed article that includes a product recess for holdinga product and a peripheral flange surrounding the product recess. Theflange of the intermediate article has a sharp terminal edge that isthen reconfigured, by cold pressing, to prevent the terminal edge fromtearing the overwrap film. In one embodiment the cold pressing step isconfigured to increase a surface area for engagement by the film toproduce a more secure and tear-resistant package.

In accordance with one embodiment of the invention, a method is providedfor producing a plastic packaging tray having a peripheral edge regionterminating in a terminal edge that is displaced out of a wrap patharound the tray, the method comprising:

-   -   providing a thermoformed plastic intermediate article for        forming the tray, the intermediate article having a peripheral        flange terminating in the terminal edge,    -   cold pressing the peripheral flange of the intermediate article        by bringing an appropriately configured compressing tool into        engagement with the terminal edge to displace the terminal edge        out of the wrap path,    -   wherein the method further comprises:        -   the peripheral flange of the intermediate article forming an            open bead disposed at an outermost periphery of the article            and a distal tail leg extending between the open bead and            the terminal edge;        -   the compressing tool engaging the terminal edge of the leg            to fully or partially close the open bead of the article and            form a cold compressed peripheral edge region of the tray            with the fully or partially closed bead at an outermost            periphery of the tray.

In one embodiment, the cold compressed peripheral edge region of thetray comprises:

-   -   a) a beaded compressed edge with the fully or partially closed        bead forming a compressed bead at the outermost periphery of the        tray;    -   b) a flat compressed edge with the fully or partially closed        bead forming a fold line at the outermost periphery and mating        engaged upper and lower flange surfaces of the tray disposed        inwardly from the outermost periphery; or    -   c) a combined beaded and flat compressed edge with the        compressed bead at the outermost periphery and mating engaged        upper and lower flange surfaces disposed inwardly from the        outermost periphery of the tray.

In one embodiment, the cold pressing step comprises:

-   -   varying a degree by which the compressing tool displaces the        terminal edge of the leg in order to vary the extent of fully or        partially closing the open bead of the article, to form a        compressed bead at the outermost periphery of the tray having a        selected outer surface area for engagement with a wrap film        disposed within the wrap path.

In one embodiment, the degree by which the compressing tool displacesthe terminal edge produces a fully closed compressed bead at theoutermost periphery of the tray.

In one embodiment, the degree by which the compressing tool displacesthe terminal edge produces a partially closed compressed bead at theoutermost periphery.

In one embodiment, a plastic packaging tray is produced by the method,wherein the thermoformed plastic intermediate article is formed with aproduct recess surrounded by the peripheral flange.

In one embodiment, the plastic packaging tray has the beaded compressededge.

In one embodiment, the plastic packaging tray has the flat compressededge.

In one embodiment, the plastic packaging tray has the combined beadedand flat compressed edge.

In one embodiment, the plastic packaging tray has a rectangular shapedoutermost periphery with rounded corners.

In one embodiment, the peripheral flange has a proximal portion forminga top wall of the article disposed between the product recess and theopen bead, and a distal portion including the open bead and distal tailleg.

In one embodiment, a dimple comprising a recess extends into an uppersurface of the top wall and protrudes from a lower surface of the topwall.

In one embodiment, the terminal edge is disposed in the tray adjacentthe lower surface of the top wall between the dimple and the outermostperiphery of the tray.

In one embodiment a wrapped and filled plastic packaging tray isproduced by the method, followed by filling the tray with a product andpositioning a sheet of plastic wrap film over the tray and productdisposed therein and pulling the sheet taut to engage the outermostperiphery of the tray in the wrap path without engaging the terminaledge.

In one embodiment, the thermoformed plastic intermediate articlecomprises a monolayer or multi-layer article, and comprises a foam,solid or a combination of foam and solid material(s).

In one embodiment, the material(s) comprise one or more of polyolefinand polyester materials, in an amorphous or semi-crystalline state.

In one embodiment, the material(s) comprise one or more of amorphouspolyethylene terephthalate, semi-crystalline polyethylene terephthalate,polypropylene, polystyrene, polyethylene, high density polyethylene, andthe article has dimensions in ranges of: thickness from 0.01 to 0.06inches, cavity depth from 0.5 to 2.5 inches, and top surface area from5.0 inches in length×5.0 inches in width to 17 inches in length to 15inches in width.

In accordance with another embodiment of the invention, an apparatus isprovided for producing a plastic packaging tray having a peripheral edgeregion terminating in a terminal edge that is displaced out of a wrappath around the tray, the apparatus comprising:

-   -   a tool body configured to hold a thermoformed plastic        intermediate article for forming the tray, the intermediate        article having a peripheral flange terminating in the terminal        edge,    -   a compressing tool for cold pressing the peripheral flange of        the intermediate article by bringing an appropriately configured        surface of the compressing tool into engagement with the        terminal edge to displace the terminal edge out of the wrap        path,    -   wherein the tool body and compressing tool are configured to        receive and displace the terminal edge of the peripheral flange,        and:        -   the peripheral flange forming an open bead disposed at an            outermost periphery of the article and a distal tail leg            extending between the open bead and the terminal edge;        -   the compressing tool surface displacing the terminal edge of            the leg to fully or partially close the open bead of the            article and form a cold compressed peripheral edge region of            the tray with the fully or partially closed bead at an            outermost periphery of the tray.

In one embodiment, the tool body and compressing tool are configured toform the cold compressed peripheral edge region of the tray comprising:

-   -   a) a beaded compressed edge with the fully or partially closed        bead forming a compressed bead at the outermost periphery of the        tray;    -   b) a flat compressed edge with the fully or partially closed        bead forming a fold line at the outermost periphery of the tray        and mating engaged upper and lower flange surfaces disposed        inwardly from the outermost periphery of the tray; or    -   c) a combined beaded and flat compressed edge with the        compressed bead at the outermost periphery and mating engaged        upper and lower flange surfaces disposed inwardly from the        outermost periphery of the tray.

In one embodiment, the apparatus is configured to:

-   -   vary a degree by which the compressing tool displaces the        terminal edge of the leg in order to vary the extent of fully or        partially closing the open bead of the article, to form a        compressed bead at the outermost periphery of the tray having a        selected outer surface area for engagement with a wrap film        disposed within the wrap path.

In one embodiment, the degree by which the compressing tool displacesthe terminal edge produces a fully closed compressed bead at theoutermost periphery of the tray.

In one embodiment, the degree by which the compressing tool displacesthe terminal edge produces a partially closed compressed bead at theoutermost periphery of the tray.

In one embodiment, a plastic packaging tray is produced by theapparatus, wherein the thermoformed plastic intermediate article isformed with a product recess surrounded by the peripheral flange.

In one embodiment, the apparatus is configured to produce the beadedcompressed edge.

In one embodiment, the apparatus is configured to produce the flatcompressed edge.

In one embodiment, the apparatus is configured to produce the combinedbeaded and flat compressed edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E are various views of a plastic packaging tray having a coldcompressed flat peripheral edge according to one embodiment of theinvention, FIG. 1A being a top perspective view, FIG. 1B a top planview, FIG. 1C a bottom plan view, FIG. 1D a front elevational view, andFIG. 1E a front elevational view of the tray filled with a product P andwrapped in a flexible plastic film wrap W;

FIG. 2 is a perspective view of an intermediate article positioned in anedge forming tool assembly for forming the cold compressed flatperipheral edge on the tray of FIGS. 1A-1E;

FIGS. 3A-3D are various views showing the steps of forming the tray ofFIGS. 1A-1E from the intermediate article and tool assembly of FIG. 2,FIG. 3A being a cross sectional view of the assembly and article in astarting position, FIG. 3B an expanded view of the edge forming areadenoted by line 3B in FIG. 3A, FIG. 3C a cross sectional view of theassembly and article (now tray) in a subsequent finish position with thefinal flat peripheral tray edge, FIG. 3D an expanded view of the edgeforming area denoted by line 3D in FIG. 3C, and FIG. 3E being a partialcut-away bottom perspective view of the final cold compressed flatperipheral tray edge;

FIGS. 4A-4B and 5 are various views of a plastic packaging tray having acold compressed beaded peripheral edge according to a second embodimentof the invention, and the steps of forming the beaded edge in anassembly similar to that of FIG. 2 but with a differently configuredcompressing tool, FIG. 4A showing a starting position (similar to FIG.3B), FIG. 4B a finish position (similar to FIG. 3D) with the final edgeincluding a bead at the outermost peripheral edge of the tray, and FIG.5 being a partial cut-away bottom perspective view of the final coldcompressed beaded peripheral tray edge;

FIGS. 6A-6G are various views of a plastic packaging tray having a coldcompressed combined beaded and flat peripheral edge with a compressedbead at the outermost periphery and mating engaged upper and lowerflange surfaces disposed inwardly from the outermost periphery of thetray according to a third embodiment of the invention, FIG. 6A being atop perspective view (similar to FIG. 1A), FIG. 6B a front elevationalview of the tray filled with a product P and wrapped in a flexibleplastic film wrap W (similar to FIG. 1E), FIG. 6C a cross sectional viewof an assembly and intermediate article in a starting position (similarto FIG. 3A), FIG. 6D an expanded view of the edge forming area denotedby line 6D in FIG. 6C (similar to FIG. 3B), FIG. 6E a cross sectionalview of the assembly and tray in a subsequent finish position (similarto FIG. 3C), FIG. 6F an expanded view of the edge forming area denotedby line 6F in FIG. 6E (similar to FIG. 3D), and FIG. 6G being a partialcut-away bottom perspective view (similar to FIG. 3E) of the final coldcompressed combined beaded and flat peripheral tray edge;

FIGS. 7A-7C are schematic views of an edge trimming apparatus forforming a terminal edge on the thermoformed intermediate article; and

FIGS. 8 and 8A-8D are various views showing an apparatus and method forvarying the dimensions of the final bead on the outermost periphery ofthe tray, and thus the surface area that lies in the wrap path W.

DETAILED DESCRIPTION

Referring now to the drawings, various embodiments of a tray having acold compressed peripheral edge according to the invention areillustrated. The reference numerals in the drawings designate identicalor corresponding parts throughout the several views.

First Embodiment

FIGS. 1-3 illustrate a plastic packaging tray and a method of formingthe tray according to a first embodiment of the invention. In thisembodiment the tray has a cold compressed flat peripheral edge regioncomprising a fold line at the outermost periphery and mating engagedupper and lower flange surfaces disposed inwardly from the outermostperiphery of the tray.

According to the method,

-   -   a thermoformed plastic intermediate article is provided for        forming the tray, the intermediate article having a peripheral        flange terminating in the terminal edge,    -   the peripheral flange of the intermediate article is cold        pressed by bringing an appropriately configured compressing tool        into engagement with the terminal edge to displace the terminal        edge out of a wrap path (in which a plastic film is wrapped        around the filled tray),    -   wherein the method further comprises:        -   the peripheral flange of the intermediate article having            opposing upper and lower flange surfaces, and forming an            open bead disposed at an outermost periphery of the article            and a distal tail leg extending between the open bead and            the terminal edge;        -   the compressing tool engaging the terminal edge of the leg            to compress the open bead and distal tail leg and forming a            cold compressed flat peripheral edge region comprising a            fold line at the outermost periphery and mating engaged            upper and lower flange surfaces disposed inwardly from the            outermost periphery of the tray.

One example of such a tray and method will now be described.

FIGS. 1A-3E illustrate a first embodiment of a plastic packaging tray 10and an intermediate article 110 that is used (as a precursor) to formthe final packaging tray 10. The intermediate article 110 (FIGS. 2-3B)is thermoformed from plastic material in the shape of a tray having acentral product recess PR, defined by a base wall 19 and sidewalls 18,and the PR being surrounded by a peripheral flange 112. The flange 112forms a top wall 14 of the article 110 (and becomes the top wall of thetray 10), the top wall having a proximal end adjacent the product recessPR, and an opposing distal end terminating in an open bead 120 locatedat the outermost periphery OP of the article. In this embodiment the topwall has a dimple 42 formed between a first top wall portion 14Aproximal the PR and a second top wall portion 14B distal to the firstportion. The dimple 42 extends as a recess 42R into the top wall uppersurface 14U and forms a protrusion 42P on the lower surface 14L of theflange top wall 14. The flange has opposing upper and lower flangesurfaces 112U, 112L and has been shaped (by thermoforming, and anoptional trimming step after thermoforming) into: a) an open bead 120disposed at the distal end of the top wall located at the outermostperiphery OP of the article, and b) a distal tail leg 122 extendingbetween the open bead 120 and a terminal edge 124. The open bead 120 anddistal tail leg 122 of the flange are subsequently displaced (foldedback and flattened) in a cold press process in the assembly 150 shown inFIGS. 2 and 3A-3D, to form a final cold compressed flat peripheral trayedge 40.

The final peripheral tray edge 40, shown in FIGS. 1A-1E and 3C-3E, has aperipheral top wall 14 (same as top wall 14 of the intermediate article110) whose upper surface 14U defines a horizontal top reference planeTRP of the tray (see FIGS. 1D-1E and 3C-3E), and a cold pressedperipheral bottom wall 16 formed by displacing (cold pressing) the openbead 120 and distal leg 122 of the flange 112 against a lower surface14L of the top wall. The lower surface 16L of the bottom wall defines ahorizontal bottom reference plane BRP parallel to the TRP (see FIG. 3C),the top and bottom walls 14, 16 being connected at the outermostperipheral edge of the tray by a fold line 44 (a flat folded edge) andwith the top wall lower surface 14L now in mating engagement with thebottom wall upper surface 16U (16 being the displaced open bead 120 anddistal tail leg 122 from the cold pressing process). In this embodiment,the flat folded edge 44 extends around the complete tray outermostperiphery TOP of the rectilinear-shaped tray 10, i.e., extendingtransversely between the TRP and BRP, and the top and bottom peripheraledge walls 14, 16 have been brought together in the assembly 150 (asshown in FIGS. 2-3D) such that adjacent mating planar surfaces (lowersurface 14L of top wall 14 and previously lower surfaces 120L, 122L ofthe open bead and distal tail leg 120, 122 (now the upper surface 16U oftray edge bottom wall 16) are near or in direct contact over all (ofsubstantially all) of their mating surfaces. In other words, the twoplanar surfaces 14L and 16U have been flattened (or crimped) together toform a flat peripheral edge 40 having a flat fold line 44 at theoutermost peripheral edge of the tray 10 with mating engaged upper andlower flange surfaces 112U and 112L (now 16U and 14L of the tray)disposed inwardly from the outermost periphery of the tray.

FIGS. 1A-1E show various views of the final tray 10 as previouslydescribed, FIGS. 1A and 1B showing the upper surface 10U of the traywith a central product recess PR (to hold a product P as shown in FIG.1E) surrounded by a peripheral edge region 40, and FIGS. 1C-1E showingthe opposing lower surface 10L of the tray. The tray PR includes a basewall 19 with opposing upper 19U and lower 19L surfaces, a shallowinwardly recessed central base area 19C (optional) in the center of thebase wall, and a lowermost standing surface 19S surrounding 19C, onwhich the tray rests (FIGS. 1C-1E). A curved peripheral area 19PA at theupper end of the base wall is joined to the lower end of the sidewalls18, thus forming a smooth lower wrap path edge around the tray, as partof the wrap path WP shown in FIG. 1E. The flat peripheral edge region 40forms a smooth upper wrap path edge around the tray, as part of the wrappath WP (see FIG. 1E). In use, the sidewalls and base form the innerproduct recess PR of the tray for holding the product between the uppersurfaces 19U and 18U of the base wall and sidewalls of the tray and thelower surface of the overwrap film W (as shown in FIG. 1E).

FIGS. 2 and 3A-3D illustrate the cold press edge forming method ingreater detail for forming the cold compressed flat folded peripheraledge region 40 of tray 10. By cold press (or cold compress, usedinterchangeably) it is meant that the no heat is required in the processof shaping the previously thermoformed flange 112 of intermediate tray110. The cold press method provides a process that is considerably lessexpensive, and does not require complex and expensive modifications tothe thermoforming mold. The intermediate tray 110 can be, for example,at room temperature (72 degrees Fahrenheit) while the flange is foldedback on itself and compressed, such that the flange 112 is permanentlydeformed by stretching it past its elastic limit but within its fracturepoint. In this process, the typically sharp edge at the distal end 124of the thermoformed article (formed during thermoforming or by cuttingafter thermoforming) is folded back towards the lower surface 112L ofthe flange 112 itself, as opposed to the tray body (i.e., the sidewalls18), and the terminal edge 124 in this embodiment is finally disposed tolie near or against the protruding dimple 42P that was previouslythermoformed on the lower surface 112L of the flange 112, between theproximal part 14A (near the sidewalls 18) and the opposing distal part14B of the top wall 14 of the thermoformed flange 112 (as shown in FIG.3B). One example of the process will now be described in greater detail.

A vertical cross section of an intermediate thermoformed article 110 isshown in FIGS. 3A-3B in an initial start position in an edge-formingassembly 150 (subsequent to thermoforming in a thermoforming mold, notshown). The intermediate article 110 (as thermoformed) includes agenerally rectilinear-shaped and planar base wall 19, lying in ahorizontal plane LSP, with a central rectilinear recessed base area 19C,the base wall having a curved periphery 19PA (lying in the wrap path WPand curved to avoid tearing the wrap film) that is smoothly connected tothe surrounding upstanding peripheral sidewalls 18. The sidewalls 18 aregenerally rectilinear-shaped (in horizontal cross section parallel tothe TRP), with opposing front and rear sidewalls disposed in a lengthdirection L, opposing left and right sidewalls disposed in a widthdirection W, and with four rounded corner sidewalls 18C connectingadjoining length and width sidewalls. The length and/or width sidewallsmay (optionally) each have structural re-enforcements in the form ofribs/recessed portions 20, and the corner sidewalls may (optionally)also have structural re-enforcements in the form of ribs/recessedportions 22. The sidewalls 18 may (optionally) also include, as anesting/stacking feature (to facilitate the spaced nesting of multiplearticles or trays in a vertical stack, and subsequent de-nesting ofindividual articles or trays from the stack of articles or trays),shoulder rims SR extending around an upper portion of the sidewalls,parallel to the TRP, and finger-tip recesses FR to further facilitategrasping and separating the nested articles or trays (see FIG. 1A).

Returning to FIGS. 2 and 3A-3D, the intermediate (previouslythermoformed) article 110 is disposed in an edge forming assembly 150between a first edge-forming tool 170 and a second edge-forming tool160. The first and second edge-forming tools are movable with respect toone another, in a displacement direction D (here transverse to the TRPof the intermediate article 110), in order to apply a displacement forceF on the terminal edge 124 of the article 110 in order to fold thedistal end of the flange 112 back onto itself. The first tool 170 has aninner sidewall surface 171 that mates with the lower surfaces 18L of thetray sidewalls; in this embodiment both 171 and 18L have complimentarytapering surfaces (at an acute angle to D), the sidewall surfaces 18Lbeing outwardly bowed at the top end (near the TRP) compared to thelower end of the sidewalls (near the base wall 19). The first tool hasdisposed at the bottom end of the sidewall 171, a forming surface 172for engaging and displacing (compressing) the flange 112. Morespecifically, the forming surface 172 includes a distal most flat endsurface 173 that engages the terminal edge 124 of the distal leg 120 offlange 112, in order to apply a force F, transverse to the edge 124,when the first tool and second tools move toward each other, to displaceand flatten the open bead 120 and distal leg 122 to a position lyingagainst the lower surface 14L of the top wall 14 of the flange 112 (inthe final position as shown in FIGS. 3C and 3D). In the final position,the terminal edge 124 of flange 112 (same as terminal edge 124 ofperipheral edge region 40 on the final tray 10) is now positionedadjacent the protruding lower surface of the dimple 42P that protrudesfrom the lower surface 14L of the top wall of the flange (now top walllower surface 14L of the tray), thus placing the typically sharpterminal edge 124 out of the wrap path in an inaccessible position(below the top wall and adjacent the protruding dimple 42). Thus, when athin plastic film wrap W (e.g., a cling wrap film comprising low densitypolyethylene) is applied around the packaging tray 10, i.e., around theoutermost periphery TOP of the tray top wall 14 and the outermostperiphery 19PA of the base wall, namely the wrap path WP as shown inFIG. 1E, the wrap W cannot engage the sharp terminal edge 124 (and thusthe film W is not torn by 124 or the peripheral edge region 40).

Second Embodiment

FIGS. 4-5 illustrate a tray and a method of forming the tray accordingto a second embodiment of the invention. In this second embodiment thetray 210 has a beaded compressed edge 240, wherein the open bead andtail leg of the intermediate article have been cold pressed to form afully or partially closed compressed bead 244 at the outermost peripheryof the tray.

According to the method,

-   -   a thermoformed plastic intermediate article is provided for        forming the tray, the intermediate article having a peripheral        flange terminating in a terminal edge,    -   the peripheral flange of the intermediate article is cold        pressed by bringing an appropriately configured compressing tool        into engagement with the terminal edge to displace the terminal        edge out of a wrap path (in which a plastic film is wrapped        around the filled tray),    -   wherein the method further comprises:        -   the peripheral flange of the intermediate article forming an            open bead disposed at an outermost periphery of the article            and a distal tail leg extending between the open bead and            the terminal edge;        -   the compressing tool engaging the terminal edge of the leg            to compress the open bead and distal tail leg and form a            cold compressed beaded peripheral edge region in which the            fully or partially closed bead forms a compressed bead            disposed at the outermost periphery of the tray.

One example of such a tray and method will now be described.

As shown in FIGS. 4A-4B, the tray 240 may be formed in an alternativeedge-forming method/assembly embodiment utilizing the same or a similarthermoformed intermediate article 110 and flange 112 disposed in astarting position of the assembly 150 (similar to that shown in FIG.3A). However, in this embodiment, there are differences in one or moreof the first and second tool shapes and/or dimensions, the speed and/ordirection of movement of the first and second tools, the intermediatearticle material composition and/or thicknesses and/or other dimensionsof the flange portions, which cause the flange 112 to form analternative peripheral edge region 240 on the final tray 210 as shown inFIG. 4B. More specifically, in this embodiment the open bead 120 anddistal tail leg 122 of the article flange 112 are displaced (coldpressed) to form a tight (closed or substantially closed) compressedbead 244 at the outermost periphery TOP of the final tray edge region240, thus disposing the sharp terminal edge 124 safely tucked away from(prevented from engaging) the wrap film W surrounding the filled tray.The terminal edge 124 is positioned substantially within thecircumference of the tight (substantially circular and closed ontoitself) bead 244, and the bead 244 lies adjacent the lower top wallsurface 14L at the distal end 14DE of the top wall 14. The wrap film Wthus engages a tightly beaded corner 244 and is kept out of contact withthe sharp terminal edge 124, as shown in FIG. 5.

Third Embodiment

FIGS. 6A-6G illustrate a tray 310 and a method of forming the trayaccording to a third embodiment of the invention. In this thirdembodiment the tray 310 has a combined beaded and flat compressed edge340, wherein the open bead 120 and tail leg 122 of the intermediatearticle have been cold pressed to form a fully or partially compressedbead 344 at the outermost periphery of the tray and mating engaged upperand lower flange surfaces 112U, 112L (16U, 14L in the finished tray)disposed inwardly from the outermost periphery of the tray.

According to the method,

-   -   a thermoformed plastic intermediate article is provided for        forming the tray, the intermediate article having a peripheral        flange terminating in a terminal edge,    -   the peripheral flange of the intermediate article is cold        pressed by bringing an appropriately configured compressing tool        into engagement with the terminal edge to displace the terminal        edge out of a wrap path (in which a plastic film is wrapped        around the filled tray),    -   wherein the method further comprises:        -   the peripheral flange of the intermediate article forming an            open bead disposed at an outermost periphery of the article            and a distal tail leg extending between the open bead and            the terminal edge;        -   the compressing tool engaging the terminal edge of the leg            to compress the open bead and distal tail leg and form a            cold compressed combined beaded and flat peripheral edge            region in which the fully or partially closed bead forms a            compressed bead disposed at the outermost periphery of the            tray and mating engaged upper and lower flange surfaces            disposed inwardly from the outermost periphery of the tray.

One example of such a tray and method will now be described.

As shown in FIGS. 6A-6B, the tray 340 may be formed in and alternativeedge-forming assembly/method embodiment, similar to that of FIGS. 2-3D.FIGS. 6A-6B are view of the final tray 310, similar to views 1A and 1Eof the first embodiment, and corresponding elements of the tray havebeen given the same reference numerals. FIGS. 6C-6F, similar to FIGS.3A-3E and with the same reference numerals for corresponding elements ofthe intermediate article, tool assembly and final tray, illustrate analternative edge-forming assembly/method embodiment, utilizing the sameor a similar thermoformed intermediate article 110 and flange 112disposed in a starting position of the assembly 150 (similar to thatshown in FIG. 3A). However, in this embodiment, there are differences inone or more of the first and second tool shapes and/or dimensions, thespeed and/or direction of movement of the first and second tools, theintermediate article material composition and/or thicknesses and/orother dimensions of the flange portions, causing the flange 112 to forman alternative peripheral edge region 340 on the final tray 310 as shownin FIG. 6E-6G. More specifically in this embodiment the open bead 120and distal tail leg 122 of the article flange 112 are displaced (coldpressed) to form a tight flat compressed bead 344 at the outermostperiphery of the final tray edge region 340, and engaged mating flangesurfaces 112U, 112L disposed inwardly from the outermost tray peripheryTOP. There is no dimple in this embodiment. The sharp terminal edge 124lies flat against the lower surface 14L of the tray top wall and issafely tucked away from (prevented from engaging) the wrap film Wsurrounding the filled tray. The wrap film W thus engages a tightlybeaded corner 344 and is kept out of contact with the sharp terminaledge 124, as shown in FIG. 6G.

ADDITIONAL FEATURES AND ALTERNATIVES

FIGS. 7A-7B illustrate one method and apparatus for trimming athermoformed article 110 to form a peripheral flange 112 having aterminal edge 124 such as that shown in the prior embodiments. FIG. 7Ais a schematic cross sectional view of one sidewall and peripheral edgeof the thermoformed intermediate article 110, having an outwardlyextending peripheral terminal flange portion 112A that extendssubstantially parallel to the top wall 14 of the article. FIG. 7B showsa cutting tool 8A, 8B that both stretches and cuts off an outermostterminal portion 112A of the flange, leaving the open bead 120 anddistal leg 122 of the peripheral flange 112 of the intermediate article110 having a terminal edge 124, as shown in FIG. 3B. Other methods oftrimming can be used, or no trimming may be used depending on thedesired shape and dimension of the article as produced in thethermoforming mold.

In various embodiments, the thermoplastic material of the tray may beone or more of polyester, such as polyethylene terephthalate (PET),including copolymers and blends of PET with other polymers andadditives, and including recycled PET and barrier materials (to gas ormoisture) and other rigid tray forming polymers. In other embodiments,the thermoplastic may be various other plastics commonly used forforming solid and rigid thermoformed trays (e.g. polyolefin polymerssuch as high density polyethylene (HDPE), with or without other polymersor additives). In one embodiment, the plastic forms a substantiallytransparent and solid polymer tray. The overwrap film may be any ofvarious thin and flexible polymer films, such as those made ofpolyethylene (PE), including low density PE. Other materials may besuitable.

In various embodiments, the thermoformed plastic intermediate articlecomprises a monolayer or multi-layer article, and comprises a foam,solid or a combination of foam and solid material(s). The material(s)may comprise one or more of polyolefin and polyester materials, in anamorphous or semi-crystalline state. The material(s) may comprise one ormore of amorphous polyethylene terephthalate, semi-crystallinepolyethylene terephthalate, polypropylene, polystyrene, polyethylene,and high density polyethylene. The article may have dimensions in rangesof: thickness from 0.01 to 0.06 inches, height (transverse to the TRP)from 0.5 to 2.5 inches, and top surface area (in TRP) from 5.0 inches inlength×5.0 inches in width to 17 inches in length×15 inches in width.

In one embodiment, the edge-forming process may include an elevatedtemperature (e.g., above room temperature of 72 degrees Fahrenheit),either as residual heat in the thermoformed intermediate tray or appliedheat prior to or during the edge-forming process. However, thisadditional heat is not required and the time and equipment costs ofheating, or maintaining a processing temperature window (range), can beavoided.

In various embodiments, the container can be of various shapes,including non-rectilinear shapes such as round or oval.

In various embodiments, the dimensions and/or orientation of the flatfolded corner 44 and/or the beaded corner 244, 344 can be controlled byadjusting the travel (speed or path) of the inner tool 170 with respectto the outer tool 160.

In various embodiments, the article flange 112 (and resulting tray topwall) may not have a dimple 42. The terminal edge 124 of the flange maystill be disposed adjacent the lower surface 16L of the bottom wall 16to avoid contact with the overwrap film W.

In various embodiments, the final position of the terminal edge 124 ofthe flange may be varied so as to be closer to or further from the lowersurface of the sidewall 18L.

In various embodiments, the final bead formed at the outermost peripheryof the tray may range from a relatively larger open bead to a relativelysmaller bead depending on how tightly the open bead 120 and tail leg 122are displaced and folded back onto the top wall 14. FIGS. 8 and 8A-8Dshow a method of varying the outer surface area OSA of the peripheralbead 244 on the tray and thus the amount of the outer surface area thatlies in the wrap path W (see FIG. 1E). As noted previously, a largersurface area in the wrap path will typically increase the tautness bywhich the wrap film clings to the tray and product, providing a moresecure sealed package. FIG. 8 is similar to FIG. 3B, showing aperipheral edge portion of the intermediate article in the edgecompressing apparatus 160, 170 in the start position, while FIGS. 8Athrough 8D show varying amounts of applied force F and/or speed oftravel S by the first tool surface 172 to the terminal edge 124,resulting in different final configurations of the bead 244 at theoutermost periphery of the final tray 10. The final bead dimension D inthe height direction, transverse to the TRP, ranges from a larger andopen bead of height D1 in FIG. 8A, through increasingly smaller beaddimensions D2, D3 and D4 as the bead becomes smaller (tighter) due togreat application of force F and/or greater speed S during the coldpressing process (FIGS. 8B-8D).

These and other variations are within the scope of the invention as setforth in the appended claims

What is claimed is:
 1. A method of producing a plastic packaging tray,the tray having a cold compressed flat peripheral edge region comprisinga fold line at its outermost periphery and mating engaged upper andlower flange surfaces disposed inwardly from the outermost periphery ofthe tray and terminating in a terminal edge that is displaced out of awrap path around the tray, the method comprising: providing athermoformed plastic intermediate article having a thermoformedperipheral flange terminating in a terminal edge, the thermoformedperipheral flange of the intermediate article having opposing upper andlower flange surfaces, and forming an open bead disposed at an outermostperiphery of the thermoformed article and a distal tail leg extendingbetween the open bead and the terminal edge; cold pressing theperipheral flange of the thermoformed intermediate article by bringingan appropriately configured compressing tool into engagement with theterminal edge to displace the terminal edge, the compressing toolengaging the terminal edge of the leg to compress the open bead anddistal tail leg and form a cold compressed flat peripheral edge regioncomprising a fold line at the outmost periphery and mating engaged upperand lower flange surfaces disposed inwardly from the outermost peripheryof the tray.
 2. The method of claim 1, wherein the cold pressing stepcomprises: varying a degree by which the compressing tool displaces theterminal edge of the distal tail leg in order to vary the extent of thecompressed flat peripheral edge region and fold line at the outermostperiphery of the tray to provide a selected outer surface area forengagement with a wrap film disposed within the wrap path.
 3. The methodof claim 2, wherein the degree by which the compressing tool displacesthe terminal edge produces a fully closed compressed bead at theoutermost periphery of the tray.
 4. The method of claim 1, wherein: theintermediate article is thermoformed from plastic material in the shapeof a tray having a central product recess PR, defined by a base wall andsidewalls, and the PR being surrounded by the peripheral flange, theperipheral flange forming a top wall of the thermoformed article (andbecomes a top wall of the tray), the top wall having a proximal endadjacent the product recess PR, and an opposing distal end terminatingin the open bead located at the outermost periphery OP of thethermoformed article; the peripheral flange having the opposing upperand lower flange surfaces that have been shaped by thermoforming (and anoptional trimming step after thermoforming) into: a) the open beaddisposed at the distal end of the top wall located at the outermostperiphery OP of the thermoformed article, and b) the distal tail legextending between the open bead and the terminal edge, and whereinduring the cold pressing step, the open bead and distal tail leg of theperipheral flange are subsequently displaced (folded back and flattened)in the cold pressing step to form the final cold compressed flatperipheral edge region of the tray.
 5. The method of claim 4, wherein: aforming surface of the tool includes a distal most flat end surface thatengages the terminal edge of the distal tail leg of the peripheralflange, in order to apply a force F, transverse to the terminal edge, todisplace and flatten the open bead and the distal tail leg to a positionlying against the lower surface of the top wall of the tray.
 6. Themethod of claim 5, wherein: a thin plastic film wrap W is applied aroundthe outermost periphery TOP of the tray top wall and the outermostperiphery of the base wall, to form the wrap path WP, wherein the wrap Wdoes not engage the terminal edge.
 7. A plastic packaging tray producedby the method of claim 1, wherein the thermoformed plastic intermediatearticle is formed with a product recess surrounded by the peripheralflange.
 8. The plastic packaging tray of claim 7, wherein the tray has arectangular shaped outermost periphery with rounded corners.
 9. Theplastic packaging tray of claim 7, wherein the peripheral flange has aproximal portion forming a top wall of the article disposed between theproduct recess and the open bead, and a distal portion including theopen bead and distal tail leg.
 10. The plastic packaging tray of claim9, wherein a dimple comprising a recess extends into an upper surface ofthe top wall and protrudes from a lower surface of the top wall.
 11. Theplastic packaging tray of claim 10, wherein the terminal edge isdisposed in the tray adjacent the lower surface of the top wall betweenthe dimple and the outermost periphery of the tray.
 12. A wrapped andfilled plastic packaging tray produced by the method of claim 1,followed by filling the tray with a product and positioning a sheet ofplastic wrap film over the tray and product disposed therein and pullingthe sheet taut to engage the outermost periphery of the tray in the wrappath without engaging the terminal edge.
 13. The wrapped and filledplastic tray of claim 12, wherein the thermoformed plastic intermediatearticle comprises a monolayer or multi-layer article, and comprises afoam, solid or a combination of foam and solid material(s).
 14. Thewrapped and filled plastic tray of claim 13, wherein the material(s)comprise one or more of polyolefin and polyester materials, in anamorphous or semi-crystalline state.
 15. The wrapped and filled plastictray of claim 13, wherein the material(s) comprise one or more ofamorphous polyethylene terephthalate, semi-crystalline polyethyleneterephthalate, polypropylene, polystyrene, polyethylene, high densitypolyethylene, and the article has dimensions in ranges of: thicknessfrom 0.01 to 0.06 inches, cavity depth from 0.5 to 2.5 inches, and topsurface area from 5.0 inches in length ×5.0 inches in width to 17 inchesin length to 15 inches in width.
 16. An apparatus for producing theplastic packaging tray of claim 1, wherein a forming surface of the toolincludes a distal most flat end surface that engages the terminal edgeof the distal tail leg of the peripheral flange, in order to apply aforce F, transverse to the terminal edge, to displace and flatten theopen bead and the distal tail leg to a position lying against the lowersurface of the top wall of the tray.
 17. The apparatus of claim 16,wherein the degree by which the compressing tool displaces the terminaledge produces a fully closed compressed bead at the outermost peripheryof the tray.
 18. A plastic packaging tray produced by the apparatus ofclaim 16, wherein the thermoformed plastic intermediate article isformed with a product recess surrounded by the peripheral flange.